Nuclear transplantation: a) Protamine is known to be involved in the "reprogramming" of the nucleus during spermatogenesis. We hope to determine whether it can exert similar effects on somatic cell nuclei, by replacing their proteins with protamine and then testing their developmental capacity by transplanting the nuclei into enucleated eggs. b) Wallace & Misulovin have recently shown that Xenopus oocytes can be grown for long periods in vitro. This leads to the possibility, which we hope to explore, of transplanting somatic cell nuclei into such oocytes and of studying their morphological and molecular properties over considerable periods of time (weeks). Analysis of the action of gene d, affecting pigmentation in the axolotl. Results thus far indicate that pigment cells do not migrate properly in d/d axolotls, and that this is due to a defective tissue environment, perhaps in the extracellular matrix used as a substratum for migration. Tissue grafting and electron microscopical studies will be continued to make certain of this conclusion. Once this is done, biochemical studies on the constituents of the matrix in normal and mutantaxolotols will be initiated.